goats showing preference for green pastures (Merchant and Riach 1994).
The interaction between nutrition, GIN infection, and LW changes has been well discussed both in sheep (Houdijk and Athanasiadou 2003) and goats (Hoste et al.
2005). It has been suggested that the severity of disease and the loss of production depend upon the intensity of infection, the host immunity, and the host´s relative nutritional status (Coop and Kyriazakis 2001).
The positive correlation coefficient between the heather percentage in the diet and the LW changes during the experimental grazing season in both stocking rates would be in agreement with our previous results (r
= 0.54; Osoro et al. 2007b), and would point again to the beneficial effects of heather availability on goats’
performance.
Implications
The high stocking rate increased the infection risk at pasture, and the supplementation of grazing goats with tannin-containing heather improved the animals’
performance, but was not able to reduce the FEC under the dry climatic conditions of the study year. Practical application of this knowledge in temperate areas would support the management of plots integrating productive improved pastures with high nutritive value (ryegrass-white clover) with natural vegetation communities including tannin-containing plants, such as heather species, as previously suggested (Osoro et al.
1999; Kahiya et al. 2003). Improved pastures would be used to improve protein and energy intake, and natural vegetation for fibre, minerals, and secondary compounds (condensed tannins) that contribute to improve animal welfare and performance to achieve sustainable goat production systems.
Acknowledgements
We thank the staff of the experimental farm for their work in the management of the animals and field sampling, and A. Mateos for her technical assistance.
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